Tactile interfaces are used in a variety of applications to enable a user operating a joy-stick like or other control device to both control movement of a point, line or solid body in at least two degrees of freedom and to provide tactile feedback to the user through the device when the guided or controlled point or body, which is generally computer simulated and displayed on a computer monitor, collides or otherwise interfaces with another surface or body. Such feedback systems can be used in a variety of applications, generally “virtually reality” applications, including generation of tool paths for various computer assisted design/computer assisted machining (CAD/CAM) applications, including computer numerically controlled (CNC) procedures, including milling, and other fabrication procedures. Such interfaces may also be utilized for graphical design and to simulate an environment for training purposes, for example to train doctors, dentists and other medical and paramedical professionals, machine operators and the like, as a controller in a variety of computer video games and in other research, industrial, medical, military and recreational applications where touch or feel is used to explore, to interface with or to act on a simulated environment. The simulated environment may be a real environment, for example a realsolid body (or bodies), which is stored in a selected digital format in the computer, or the simulated environment being interfaced with may be an unknown environment which is randomly or arbitrarily generated for training or other purposes.
Existing haptic interfaces have been limited in that most have been capable of operating in only a limited number of degrees of freedom, rather than providing full five or six degrees of freedom capability and, more particularly, for interfaces capable of operating in multiple degrees of freedom, have been capable of providing only point contact with a body, not real full-body contact between bodies which have complex geometries. Thus, with such interfaces, it is not possible to simulate many real world environments.
Another factor which is particularly useful in CAD/CAM and in training applications is for the user not only to be able to feel what they are doing, maintaining desired contacts while avoiding undesired collisions, but also to be prompted to maintain the tool or other guided/controlled body in a proper orientation with proper portions of the bodies in contact and to receive tactile feedback through the haptic interface tool when the user deviates from one or more of the desired factors. The same can be true for the force applied when two bodies are brought together, for example when a drill is brought in contact with a surface to be drilled. The force applied to the tool can influence things such as heating of the contacting bodies as a result of friction, depth of cut, torque on the drill and time to complete the job. Too much force or too little force can adversely affect one or more of these factors, and it is therefore desirable that the user be able to feel when a proper force is being applied. It is therefore desirable that a computer controlled haptic interface also provide feedback to a user through the interface device to indicate when the user is at a proper orientation, when proper points of the bodies are in contact and/or when an appropriate force is being applied and to provide feedback to the user when the user deviates from the desired factors. This feedback force can increase gradually with increased deviation from the desired factors or the system can provide a “snap-fit,” which provides a force to pull the bodies into a desired contact when they are within a selected distance of each other and resists movement which would take the bodies out of contact. The feedback force could also be tailored to simulate other events/conditions for a selected application.
Finally, it is generally required that haptic feedback systems provide real time performance; for example sampling and responding at 1000 Hz, even with the enhanced features indicated above. Haptic interface systems providing most of the capabilities indicated above do not currently exist in the art, and there is certainly nothing providing the indicated functions while still operating in real time.